You are correct that septic systems require special considerations when considering the discharge from school science areas. We are not aware of any resource that specifically addresses this situation. However, we can provide some links to general resources and waste minimisation strategies.

Septic systems work using anerobic microbes and physical settling process to clarify the waste water. The addition of excessive water or very acid or alkaline solutions can dilute or destroy the microbes. Many laboratory chemicals are hazardous to the environment. Anything chemical that is toxic or hazardous to the environment such as those classified as a Dangerous Goods class 6 or 9, should definitely not be disposed down the sink.

Science ASSIST recommends that no chemical waste should be disposed of into a septic system as it has the potential to disrupt the bacterial processes within the system and harm the environment. It would be acceptable for the rinsing of glassware of most water-soluble chemicals to be disposed in the septic system as it would involve only trace amounts of chemicals. Very small quantities of acids/bases could be diluted and neutralised, but the total volume of liquid should not be excessive. It would be wise to place caution notices advising of this above the sinks in the laboratories.

The best approach is to minimise the amount of waste produced and arrange for all hazardous waste to be disposed by a chemical waste contractor. As far as practicable, we suggest conducting activities on a microscale where possible to reduce the quantity of chemical waste produced,

General information regarding septic tanks

The following documents are generally written to address requirement for households and may contain state specific requirements. They explain how septic systems work and may have some general comments regarding waste that is unsuitable for septic systems that could be applied to schools.

National Research Council (US) Committee on Prudent Practices in the Laboratory. Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards: Updated Version. Washington (DC): National Academies Press (US); 2011. 8, Management of Waste. Available from: https://www.ncbi.nlm.nih.gov/books/NBK55885/